SHAFAQNA – Imam Baqer (AS) was asked: For what purpose, Lady Fatima (AS) is called Zahra? Imam (AS) replied: For this reason that Allah (SWT) has created that Lady (AS) from God’s magnificent light, and when that light started shining, the skies and the earth have been illuminated, and the eyes of the angels were filled with that light’s rays; and all angels prostrated to God and said: O’ Allah (SWT), O’ our God, what is this light? Allah (SWT) sent revelation to them: This is a light from Allah (SWT) which has been placed in God’s sky and has been created from Divine Magnificence and God will bring it out of the back of a Prophet (PBUH) from among God’s prophets; the Prophet of Islam (PBUH) who is the highest ranking among all prophets; and from this light, Imams (AS) will come out, who will rise to God’s Command, and will lead and guide people to the truth; and after the end of the time of the revelation, God will appoint them as Divine Caliphs on earth .
 Kashful Qommah, Vol. 2, Page 21.